As an image display device using a current-driven light-emitting element, an image display device using organic electroluminescence (EL) elements is known. The organic EL display device using self-luminous organic EL elements is suitable for making a thin device without the need of a backlight which is necessary for a liquid crystal display device. Moreover, since there is no restriction on a viewing angle, the organic EL display device is expected to be put into practical use as a next-generation display device.
Patent Literature 1 discloses a circuit configuration of a pixel circuit in an active matrix organic EL display device.
FIG. 9 is a circuit configuration of a pixel circuit 510 in a conventional organic EL display device disclosed in Patent Literature 1.
The pixel circuit 510 includes a light-emitting element 515 that is an organic EL element, a capacitor 513, a driving element 514 that is an n-type thin-film transistor (TFT) having a gate connected to a first electrode 5131 of the capacitor 513 and a source connected to the light-emitting element 515, a third switching element 519 which switches between conduction and non-conduction between a source of the driving circuit 514 and a second electrode 5132 of the capacitor 513, a first switching transistor 512 which switches between conduction and non-conduction between a reference power source line 520 and the first electrode 5131 of the capacitor 513, and a second switching element 511 which switches between conduction and non-conduction between a signal line 516 and the second electrode 5132 of the capacitor 513.
Since the pixel circuit 510 can be driven such that current flowing in the driving element 514 is always only via the light-emitting element 515, the steady-state current does not flow in the reference power source line 520 and the signal line 516.
Therefore, it is possible to hold an accurate potential which is not affected by a change in voltage drop and a change in driving voltage of the light-emitting element 515, at both end electrodes of the capacitor 513 having a function of holding a voltage between the gate and the source of the driving element 514, with the result that it is possible to realize high-definition image display reflecting image signals.